Neutralization of mahogany sulfonic acids



NEUTRALIZATION F MAHOGANY SULFONIC ACIDS Manley Kjonaas, Hammond, Ind., assignor to Sinclair Refining Company, New York, N. Y., a corporation of Maine No Drawing. Application February 15, 1956 Serial No. 565,547

2 Claims. (Cl. 260-504) This invention relates to neutralization of mahogany sulfonic acids. More particularly, this invention relates to a process for the neutralization of oil-soluble mahogany sulfonic acids to produce basic barium mahogany sulfonates.

It is characteristic of lubricants employed in internal combustion engines such as compression-ignition engines and spark ignition engines, to deteriorate under normal conditions of use and form corrosive bodies, sludge, lacquer, varnish and similar contaminants in the engines. These contaminants are known to be deleterious to efficient operation and reasonable engine life. To overcome the effect of deterioration products, it has become normal practice to employ detergent additives in lubricating oils. A detergent additive appears to impart properties to the lubricating oil which enable it to retain contaminants in suspension or dispersed in oil so they will not settle out or adhere to metal surfaces and promote wearing, scufling, scoring and sticking of metal parts.

Of the numerous detergent additives known, a highly efiicient group and possibly the most extensively used in commercial oils comprise the alkaline earth metal salts of oil-soluble mahogany sulfonic acids. While the simple neutral salts evidence detergent action, it is now recognized that basic alkaline earth metal mahogany sulfonates are more desirable than the neutral or near-neutral sulfonates because high basicity apparently results in greater detergency.

Mahogany sulfonic acids are commercially derived from the treatment of mineral oils, such as lubricating oil fractions and gas oils, with fuming sulfuric acid or oleum during the manufacture of highly refined lubricating oils, medicinal oils and technical white oils. The sulfonation treatment results in two layers, a lower layer comprising an acid sludge and an upper layer comprising acid oil and containing the oil-soluble or mahogany sulfonic acids. Sulfonic acids can also be obtained by treating a suitable oil fraction with sulfur trioxide, or dually treating the oil with oleum or acid and sulfur trioxide. The oil which is sulfonated can contain solvent materials, for example, kerosene. The sulfonic acids however obtained are then neutralized with a suitable basic material to obtain the desired sulfonate. While it is common in the art to refor to the sulfonate forming step as neutralization, the usual commercial practice employs an excess of neutralization agent to afiord a product which is highly basic. Neutralization as employed throughout this disclosure is intended to indicate that at least about 1.5 equivalents of base are reacted with the acid oil to provide the basic sulfonate.

Some of the criterion established for a satisfactory sulfonate intended for use as a detergent additive, in addition to detergency, include color, base number, metal content and compatibility with a broad range of lubricatnited States Patent 0 l Patented Apr. 22, 1958 ing oils and other additives which normally are used. Superiority in each of the characteristics is desired; this however is difiicult to obtain in practice since, among other things, economics of the product must be considered. The present invention relates in particular to a process for the preparation of basic barium mahogany sulfonates which are characterized by good color, basicity, metal content and compatibility.

In typical batch neutralization processes where a water solution of barium hydroxide is added to the sulfonic acids and stirred, reaction is generally complete in a few hours. To drive ed the Water added, water of neutralization and water of hydration, the usual batch operation requires at least about three days. In laboratory scale batch operations, boil-off requires about 3 to 4 hours. If settling be attemped instead of heating to drive oft the Water, the yield and the barium content are objectionably low. It has now been discovered, surprisingly, that by carefully controlling the quantity of water entering the reaction so that a defined quantity of water is present in the resulting aqueous phase at the termination of neutralization of sultonic acids with barium hydroxide, desirable basic barium mahogany sulfonates are produced in an economical manner and substantially all of the water present can be separated by mere decantation in a very short time. The product is obtained in good yield and the product is characterized by a good color, high base number and metal content and by compatibility with lubricating oils containing additives, for example zinc dithiophosphate.

The following examples will serve to illustrate the invention. In these examples basic barium mahogany sulfonates are produced by reacting a slurry of barium hydroxide with an acid oil obtained by sulfonating an oleum pretreated gas oil with sulfur trioxide while the pretreated gas oil is diluted with about three parts of kerosene. The same procedure was employed for each run and was as follows: measured amounts of kerosene solution of acid oil, water and barium oxides are charged to a one liter Magne Dash autoclave. The autoclave is closed and heated to reaction temperature While mixing the reactants. The autoclave is held at the reaction temperature while mixing its contents the required length of time to complete the reaction. The contents of the autoclave are then settled. The resulting oil layer is withdrawn and allowed to flash into a warm three-necked flask to obtain a substantially anhydrous sulfonate in kerosene solution. The solution is filtered and the kerosene is removed by vacuum distillation to give the desired product. The batch neutralization runs reported in the following examples are procedures which follow actual commercial runs employing water boil-oflf. Boil-cit has been recognized as the superior batch-type procedure.

EXAMPLE I For these runs 590 grams of an acid oil having an acid number of about 7.0, about 23.6 grams of barium oxide and varying amounts of water were employed. The neutralization mixture was settled at the reaction temper ature for about 10 minutes after reaction and a clear aqueous barium-containing solution was withdrawn. The organic phase-was flash dehydrated and filtered, after which the kerosene solvent was removed by vacuum distillation. The resulting sulfonate product was analyzed for barium content and the water-barium hydroxide layer was analyzed for percentage of water. The water present in the product water phase and its effect was observed. Two different batches of acid oil were employed as indicated.

These runs show that the concentration of barium hydroxide in the aqueous phase after neutralization, or conversely the concentration of water in this phase has a great influence on the resultant product. From these data, it can be seen that a water content of about 40 to 55% in the water-barium hydroxide phase results in a product having a satisfactory barium content not materially above that obtained in a conventional batch neutralization process. At this concentration, the phase is easily handled as a liquid with the barium content in solution and without the necessity or employing higher temperatures to increase solubility of barium hydroxide as would be necessary at higher concentrations. T hese data also show that for lower quantities of water a higher barium content is obtained (note runs 2 and 3). However, the sulfonate products from runs 2 and 3 were unstable and were not compatible in a lubricating oil containing zinc dithiophosphate while the sulfonates from runs 21, 29 and 20 were both stable and compatible.

EXAMPLE II tralization was observed.

Table II Acid Oil Run No. Tempera- Percent ature, F. Barium These results show that above 250 F. the temperatures of neutralization has only a very small effect upon barium content of the suifonates produced; barium content improves only about 1% for each 25 increase in temperature. Temperatures upwards of about 500 to 600 F. can be used, when the pressure is sufiicient to maintain liquid phase. However, no advantage has been observed with temperatures above about 300 F. while pressure requirements do increase, so it is preferred to employ a temperature of about 250 to 300 F. Tests of products for compatibility with a lubricating oil containing zinc dithiophosphate show that those made at 250 to 275 F. were best in compatibility. From a large number of runs it was determined that products obtained with a temperature of about 250 to 300 F. were entirely satisfactory.

droxide present was determined. The quantity of barium hydroxide present was measured as the percentage of theoretical needed for neutralization. Suflicient water was employed in each instance (batch runs excepted) to obtain a clear aqueous barium-containing phase having a water content of about 40 to 55%. The data obtained are:

Table III N eutrali- Theo- Acid Oil Run N0. zation retical Percent Temp, Percent Ba F. Ba Used Batch Neutralized 270 300 7. 50 8 350 1, 200 8. 15 300 400 8.05 Batch N eutralizcd 270 300 5.90 36 300 850 6. 50 300 600 6. 69 300 400 6. 42

These runs show that actual quantity of barium hydroxide present has little eilfect upon the resulting prodnet, as measured by barium content. From data obtained in additional runs it was determined that 900 to 1500% of the theoretical quantity of barium hydroxide needed was very eitective in producing sulfonates which had the requisite properties and still prevented the water of reaction from over-diluting the resulting aqueous phase. A quantity of about 1200% of theoretical is preferred since control of water content of the aqueous layer is easier than with lesser amounts. Excess barium hydroxide can be recycled for reuse and thus does not constitute a loss to the process. Usually, the decanted solution of barium hydroxide is dehydrated slightly to allow for dilution with water of neutralization. Since the decanted solution is a clear liquid it is easily metered to the reaction zone to facilitate greatly the maintenance of the proper amount of Water in the neutralization zone.

In other runs to determine the effect of mixing and settling times, it was found that these conditions do not affect barium content to a significant amount when employing the optimum quantity of barium reactant and suificient water to result in a water concentration in the aqueous phase of about 40 to 55%. For maximum economic utilization of equipment it is desirable to limit mixing and settling times and for these reasons it is preferred to extend these steps only for about 15 minutes. Settling can be conducted in any of the apparatus presently conventional for settling. The temperature maintained in the settling zone should be at least sufficient to retain the barium compound solubilized. Where high temperatures above the boiling point of water are employed, it is necessary to keep pressure on the system to insure liquid phase conditions and avoid water loss. Thus, it is preferred to settle the reaction mixture at the temperature and pressure of reaction and always above about F. to insure solubility of the barium materials.

One of the most significant advantages of the present invention is that by controlling the water content as indicated, an essentially clear aqueoussolution of barium hydroxide results as the aqueous phase, as distinguished from a slurry. Thus, the largest portion of the unreacted barium is readily removed from the desired product. More important, substantially all of the free water is readily separated from the product by the act of separating the phase. The extended periods of time consumed by the boil-oii procedures of the prior art are no longer necessary as settling is usually complete in about 5 to 15 or 20 minutes. Other advantages attending upon this procedure include lowered requirements for maintenance of filters as only a minor amount of solids will be deposited upon filtering the product; further, as substantially all Water is removed in settling, other economies appear in flash dehydrating the product to the desired commercial state since very little water remains at this point.

From the preceding examples it can be seen that the assnsse Acid No. M.W.Ba and M. W. KOHX e. g./mol

Assuming 200% BaO reacts then gms. BaOXfraction unreacted=unreacted BaO in gms.

BaO+H O Ba(OH) g. BaO unreacted M. W. of BaO needed for conversion of BaO to Ba(OH) XM. W. of H O=y guns. of water m=fraction Of WfitEBI desired in Water phase where z is the gms. of free water at end of reaction needed to result in the selected fraction of water being present in the aqueous phase.

z+y=gms. water total A typical calculation for a charge of 1000 gms. of acid oil having an acid No. of 7 and employing BaO in an amount of 1200% of the theoretical quantity where about 200% reacts is as follows:

1000 =11a6 gmS. BaO

114.6X/6=95.5 gms. BaO unreacted 1s=112 g. H O needed to convert BaO to Ba(OH) If 50% water is wanted in aqueous phase:

z=106.7 gms. water in aqueous phase for a 50% water content 106.7+11.2=117.9 gms. water total The method of the present invention is essentially an autoclave neutralization of an oil-soluble acid oil to produce a basic barium mahogany sulfonate in the presence of a controlled amount of water. In addition to the advantages disclosed above, the present method is further advantageous in that it lends itself to adaptation to a continuous process. Thus, an acid oil and a barium oxide slurry can be fed continuously to a first mixing zone maintained at a temperature of about 180 F. to 220 F. and a pressure sufiicient to maintain a liquid phase. The resulting neutral barium mahogany sulfonates containing water and excess barium hydroxide are continuously removed from the first mixer and introduced into a second Zone maintained at the desired higher reaction temperature, for example, 250 to 300 F. At this higher temperature, the neutral sulfonate apparently reacts with further quantities of the hydroxide present whereby the basic salts are produced. The mixture is then passed to a settler and separates into two phases, the upper phase: being the sulfonate material and the lower being an aqueous barium hydroxide solution. The lower phase is withdrawn and can be recycled for use in the process again after suitable adjustment of the water content while the upper phase is passed to a product recovery system which generally comprises a filtering zone and a flash dehydration zone. As the second neutralization zone is maintained at elevated pressures, for example about 20 or more p. s. i. g., drying of the product by flash dehydration can merely involve introducing the sulfonate phase into a tower maintained at the same temperature but at lower pressures. The barium sulfonate product is purified by filtration followed by vacuum distillation of the kerosene.

What is claimed is:

l. A method for producing basic barium mahogany sulfonates which comprises contacting a sulfonic acid mineral oil, water and barium hydroxide at a temperature above about 250 F. and at a pressure sufiicient to maintain substantially liquid phase conditions, said water being present in an amount sufficient to result in a water content in the resulting aqueous phase of about 40 to weight percent, settling the reaction product to obtain an aqueous phase, and separating the aqueous phase to recover the resulting basic barium mahogany sulfonates as product.

2. A method for producing basic barium mahogany sulfonate which comprises heating'a mixture of a sulfonic acid mineral oil and an aqueous slurry of barium hydroxide in a first zone at a temperature of about to 220 F., passing said mixture to a second zone maintained at a temperature of about 250 to 300 F. and at a pressure sufiicient to maintain the mixture in the liquid phase, passing the resulting mixture to a settling zone to form an aqueous phase and a sulfonate phase, recovering the produced sulfonates, and maintaining a quantity of water in said slurry of barium hydroxide suflicient to result in a water content of said aqueous phase of about 40 to 55%.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD FOR PRODUCING BASIC BARIUM MAHOGANY SULFONATES WHICH COMPROSED CONTACTING A SULFONIC ACID MINERAL OIL, WATER AND BARIUM HYDROXIDE AT A TEMPERATURE ABOVE ABOUT 250*F. AND AT A PRESSURE SUFFICIENT TO MAINTAIN SUBSTANTIALLY LIQUID PHASE CONDITION, SAID WATER BEING PRESENT IN A AMOUNT SUFFICIENT TO RESULT IN A WATER CONTENT IN THE RESULTING AQUEOUS PHASE OF ABOUT 40 TO 55 WEIGHT PRECENT, SETTLING THE REACTION PRODUCT TO OBTAIN ANAQUEOUS PHASE, AND SEPARATING THE AQUEOUS PHASE TO RECOVER THE SESULTING BASIC BARIUM MAHOGANY SULFONATES AS PRODUCT. 